tshin, your son probably has figured out by now that when he has certain behaviors he will get suspension and if he likes it, he might end up there again if the teacher's niceness wears off again, so it would be nice to finish out the year in a different classroom. My DD was in 2nd last year and by Jan. I wanted her across the hall, to a teacher that was always trying to help DD in the hallway etc. and was willing to have her move over. The principal said "we don't change classrooms" citing policy, no exceptions. After a meeting DD's teacher would be better for a couple of weeks and then slide again.
When my DD was in K (different school, different state), she absolutely hated being in the classroom and figured out pretty quickly that if she did certain things, she'd end up in the principal's office where it was quiet, and she'd chat with visitors. So at her high point she got herself there up to 5 times per day. Also, she faked a speech issue and insisted she had to leave with the other kids who were going to speech therapy. She tried that for a couple of weeks.
I took her out of K mid-year and homeschooled until 2nd grade, new state, new school, not much improvement except that she handles things better.
But we're having her tested again and there has to be alot of change for next year for me to agree to keep sending her.